Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Suggested Citation:"3 Toxicological Testing of Dispersants and Dispersed Oil." National Research Council. 1989. Using Oil Spill Dispersants on the Sea. Washington, DC: The National Academies Press. doi: 10.17226/736.

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

3
Toxicological Testing of
Dispersants and Dispersed Oil
This chapter describes what is known about biological espe-
ciaBy toxicological effects of dispersants and dispersed oils from
laboratory studies; reviews the evidence on oil-induced damage to
organisms and how it is modified by dispersant use; and notes the
applications and limitations of this knowledge (Figure 3-1~. Experi-
ence with of} spill dispersants over the years has resulted in less toxic
formulations. However, some questions pertaining to the effects of
dispersants with and without oil remain, and they are addressed
throughout this chapter.
OVERVIEW OF TOXICOLOGICAL TESTING
Toxicity, the potential of a material to cause adverse effects in
a living organism, is a relative measure (see GIossary). Estimates of
toxicity depend on many experimental physicochemical and biolog-
ical factors. In addition, there are many different testing methods
and variations in the products tested. A related problem has been
the uncertain applicability of toxicity data from one species in one
body of water to another species or area. For example, are species'
sensitivities to dispersed oils in New England waters applicable to
Texan waters? This question, which is of concern to regulators and
industry, is addressed in this chapter.
81

82
USING OIL SPILL DISPERSANTS ON THE SEA
DISPERSANTS PETROLEUM OILS
Physicochemical Characteristics Physicochemical Characteristics
Effectiveness of Dispersants Volume, Location of Spill
Toxicology of Components Toxicology of Key Constituents
Exposure of Biota to
Dispersed Oils
l Seawater Temperature
|1
IMPACTS OF DISPERSED OILS
Specific Habitat Vulnerabilities (exposure)
Sensitivities of Individuals and Populations (response)
Community Recovery Potential (recovery)
FIGURE ~1 Factors to consider in the assessment of biological effects of dispersed
oil in marine environments.
The objectives of toxicity testing of dispersants and dispersed
oils in the laboratory are:
~ to provide data on relative acute toxicities of effective prod-
ucts to commonly used test species under standardized conditions so
that dispersant users have a basis for selecting effective and accept-
ably Tow toxicity products;
· ~ . ~ ~
co assure anal c~lspersants do not significantly increase the
acute and chronic toxicities of dispersed petroleum hydrocarbons;
and
.
to determine factors that modify dispersant toxicity, or en-
hance or ameliorate of] toxicity under natural conditions.
Different types of toxicity tests can satisfy these objectives. Tests
are chosen to detect potentially harmful products both rapidly and
reliably. They are not intended to be ecologically realistic or to
predict effects in the field.
In measuring toxicity effects of oils, exposure comparisons may
be made using the integral of concentration multiplied by time of
exposure to 50 percent mortality LC50 (Anderson et al., 1980~; the
results of exposure tests are usually expressed as mg/liter per day
or per hour. Since concentration may also be stated in approximate
terms as parts-per-million (ppm) or parts-per-billion (ppb), and the
exposure period as hours or days, some data on dispersed of]

TOXICOL O GICA L TESTINrG OF OIL DISPERSA NTS
83
presented in this chapter will be stated as ppm-hour (ppm-hr) or
ppm 1-day or 2-days. This allows a comparison to be made between
different exposures used by different investigators who use the same
analytical techniques. The exposure-time expression also allows an
exposure to be expressed as concentrations change rapidly in the
field. This concept probably holds during time periods from 1 hr to 4
days for oil and dispersed of} exposures. The use of ppm-hr assumes
that organisms wiB respond in the same manner to a tox~cant if
exposed, for example, to 20 ppm for 1 hr or to 1 ppm for 20 hr. The
concept is approximately valid for some of the data shown in this
chapter.
There are obvious limits to this concept. If the time is short and
the concentration high, the organism may be killed immediately. If
the time is long and the concentration correspondingly lower, many
organisms can tolerate, adapt to, or metabolize hydrocarbons and
~~spersants and survive and recover without apparent adverse effects.
This concept has long been used in radiation exposures. It was
proposed and used by Anderson et al. (1980, 19843, and McAuliffe
(1986, 1987a) used the concept to compare laboratory bioassays that
actuary measured the dissolved hydrocarbons in the water-soluble
fraction and chemically dispersed of! exposures with those measured
in the field.
O
Toxicological Testing Methods
Considerable attention has been paid, especially by regulatory
agencies, to
the choice of suitable exposure regimes (static, continuous
flow);
test species;
acute versus chronic testing;
influence of modifying factors; and
standardized testing protocols.
International workshops on these issues have been held by the
United Nations Food and Agriculture Organisation (FAD) and the
United Nations Environmental Programme (UNEP). Work from the
United Kingdom has included Shelton (1969), Perkins (1972), and
Beynon and Cowell (1974~. Work from the United States has in-
cluded Tarzwell (1969, 1970), ZiDioux et al. (1973), and Becker
et al. (1973~. Canadian work has included Mackay et al. (1981),
Wells (1984), and workshops leading to the Canadian Dispersant

84
USINrG OIL SPILL DISPERSANTS ON THE SEA
Guidelines, 2d edition, Environment Canada (1984~. FAD has been
represented by White (1976) and UNEP by Thompson (1980 and
private communication).
It is difficult to compare disperant formulations or sensitivities
of different species, unless such work is conducted comprehensively
in qualified laboratories (Doe and Wells, 1978; Wells, 1984; Wilson,
private communications. Furthermore, information obtained using
rigorously controlled and standardized testing protocols is desirable
for reliable interpretation of toxicological information. Major com-
ponents and trace contaminants should be known and exposures
verified by analyzing the water in which the organisms are exposed.
Fish, arthropods (usually decapod crustaceans), mollusks (pele-
cypods), annelids (polychaetes), and algae have been the favored
test species. Some researchers have also studied sensitive life stages;
behavioral, biochemical, and developmental responses; and multi-
species interactions, either acute or chronic. Testing of current for-
mulations can be acute (i.e., short term), single-species, lethal, or
sublethal; it is usually done in static rather than flowing systems,
and at ambient temperatures. Some testing includes standard sam-
ples or reference tox~cants.
Dispersant toxicity thresholds are most often reported as nom-
inal concentrations total amount of dispersant or oil divided by
the total volume of water in the experimental chamber- rather than
measured concentrations of materials to which organisms are actu-
ally exposed. This can lead to major errors in some cases. For some
water-immiscible formulations at high concentrations, dispersant in
the bioassay chambers can separate into a floating and dispersed
upper-surface layer, several millimeters thick, and a dissolved sub-
surface fraction during the tests. For example, BPllOOX in static
tests separates like this immediately. Expressing the LC50 or EC50
on the basis of nominal concentration then gives a higher (and in-
correct) value than if the water-soluble fraction were analyzed and
used as the basis. Thus the toxicity of a water-soluble material may
be underestimated. The same problem arises because of the immis-
cibility of water and dispersed oil (as discussed later in this chapter).
For some dispersant formulations, this is an important but generally
unrecognized source of error for toxicity estimates.
Dispersant Screening Procedures for Toxicity: Considerations
The qualities of a good laboratory screening test are that it
is easy to perform and control, and it is reliable, reproducible, and

TOXICOL O GICA L TESTING OF OIL DISPERSA NTS
85
adequately sensitive. Because its purpose is to determine the relative
toxicity of one dispersant versus other previously tested dispersants,
practicality and known sensitivity are weighed against ecological
realism. Screening tests are usually conducted with a single species,
but do not yet attempt to simulate interactions of two or more
species, that is, community responses (Cairns, 1983; Mount, 1985~.
Screening tests can include
various test species and life stages;
response parameters other than mortality;
various test materials;
different exposure modes;
varying length of exposure; and
various pass-fai] criteria.
Laboratory tests are poor simulations of natural conditions because
they are conducted under standard controlled conditions. Gener-
aBy, this means exposing animals in the laboratory to more or less
constant concentrations for 2 to 4 days, while in the ocean initial
concentrations of dispersants and dispersed of} would be diluted pro-
gressively and generally rapidly.
Because the effectiveness and toxicity of a dispersant may be
positively correlated, screening tests should consider both criteria in
sequence (Bratbak et al., 1982; Doe and Wells, 1978; Mackay and
Wells, 1983; Nes and Noriand, 1983; Norton et al., 1978; Swedmark
et al., 1973~. Both criteria have already been considered together
when evaluating dispersants for government agencies (Anderson et
al., 1985; Aranjo et al., 1987; Environment Canada, 1984~. Screen-
ing tests should accurately evaluate and accommodate the possibly
greater acute toxicity of more effective dispersants.
For improved accuracy and utility of hazard assessments, future
screening toxicity tests should consider the above factors, the physical
chemistry of the dispersant solutions, and the responses of the test
organisms during short exposures.
Dispersant Screening Procedures in Canada, the
United States, and Other Countries
Until 1982, most countries used a combination of dispersant
and dispersed oil tests, of! and dispersed of} tests, or tests with ah
treatments (WeBs, 1982a). The primary concern was to evaluate the
toxicity of oils upon dispersal. Such an approach was particularly

86
USING OIL SPILL DISPERSANTS ON THE SEA
supported by the United Kingdom's sea and beach test.* However,
the inclusion of oils in dispersant tests is experimentally complex
because it introduces a new set of variables associated with the oil and
is subject to errors in interpretation because of immiscibility (Welis,
1982a; Wells et al., 1984a,b). Yet most countries, out of concern
about dispersed of} effects and joint toxicity of of} and dispersant
constituents, have included both of! and dispersant in their tests.
Some countries screen dispersants only (e.g., Australia, Canada,
several Asian countries). At least 10 countries employ a toxicity
screening test for dispersants or dispersed oil: Australia, Canada
(linked to effectiveness test), France, Hong Kong (modified U.K. sea
test), Japan, Norway (modified U.K. sea test), Singapore (modi-
fied 1970s Canadian test; Environment Canada, 1973), South Africa
(modified U.K. sea test), United Kingdom, and the United States.
Brazil (Aranjo et al., 1987), Nigeria, the Philippines, and Sweden are
also developing testing approaches (SchaTin, 1987~. Screening meth-
ods and status are listed in Tables 3-1, 3-2, and 3-3; of particular
note are procedures for Australia, Canada, South Africa, the United
Kingdom, and the United States (Table 3-1; reviewed in detail by
Moldan and Chapman, 1983; Thompson, 1985; and WeDs, 1982a). A
number of other countries are thought to be doing tests.
The most frequent combination of test materials are dispersant,
oil, and dispersed oil, that is, dispersant and oil mixture (Table
3-3~. Most tests use seawater, and lethality is the usual toxicity re-
spouse. Many different test species are used, with little uniformity
among countries. Both indigenous and standard species have been
selected, such as local shrimp and Artemia, and in most countries lo-
cal species are used as the standard (rainbow trout, Salmo gairdneri,
in Cana(la; brown shrimp, Crangon crangon, in the United Kingdom;
and mummichog, Fundulus heteroclitus, in the United States). Most
countries have pass-fai} criteria, but they vary. When dispersed of! is
tested in the laboratory, of! composition is variable and differs from
place to place, the water-soluble fraction is normally not separated,
and hydrocarbon exposures are normally not measured. Hence, the
same dispersant submitted to different countries for approval may be
subjected to quite different toxicity screening methods and pass-fai!
· ~
criteria.
*The United Kingdom screens for effectiveness first, and dispersants that pass go
onto the toxicity-testing phase. The work is conducted in two laboratories and is a
phased approach rather than a linked approach.

96
USING OIL SPILL DISPERSANTS ON THE SEA
The lack of a standardized approach displays a lack of consensus
about screening test objectives. For example:
· The United Kingdom attempts realism in both its sea and
beach tests, one with of} exposure in the water column and one sim-
ulating exposure to a beach application of dispersant, respectively.
However, the sea test ignores the experimental complexity of prepar-
ing and controlling the of] preparation, and the beach test assumes
that dispersants will be used directly on rocky shorelines.
The U.S. test covers all treatments but simply lists the tox~-
city data without interpreting it for use by the on-scene coordinator
(OSC).
Canada's test is linked closely to the effectiveness test through
a formal decision framework, but it only screens the dispersant using
a single-species freshwater fish test.
The state of Sao Paula in Brazil is adopting an approach sim-
ilar to Canada's, ultimately screening the dispersant with a valuable
indigenous shrimp.
To date, only Canada and Brazil link effectiveness and toxicity
screening tests in a formal decision-making framework, although the
United States is considering such a linkage based on Anderson et al.
(19851. Yet, as pointed out by Thompson (1985), it is important
~ ,
for ah countries to recognize Contemporary problems arising from
the development of effective third-generation dispersants and more
accurate methods for determining the toxicity of oils" in the design
of their toxicity screening tests.
There are significant advantages to screening only the dispersant
formulation, but an international consensus on the key treatments to
test has not yet been reached. A consensus on methods would allow
reliable comparisons of data from one country to another.
TOXICITY OF DISPERSANTS
This section summarizes the aquatic toxicology of dispersant
components and commercially available dispersants. Data are re-
ported for early formulations, as wed as second- and third-generation
dispersants that generally are less acutely toxic than earlier products.
Toxicity is a relative measure that is influenced by many fac-
tors, particularly concentration, duration of exposure, and type of
organism. Most of these experiments use concentrations and expo-
sure durations that substantially exceed expected field exposures.
Nevertheless, the following factors are important to understand:

TOXI COL O GI CA L TES TING OF OIL DISPER SA NTS
i:
97
· the risks of misapplication of dispersants;
· the environmental fate and effects of dispersant materials
added to ocean waters to treat of} spills;
· the range of responses in different species and to different
formulations and to different environments; and
· which components contribute most to toxicity in order to
mprove formulations.
Acute Toxicity of Components
Knowledge about the toxicity of the primary components of dis-
persants would assist in evaluating dispersant toxicology and the
toxicities of dispersed oils. Ad surfactants are toxic at high concen-
trations. Many surfactants have unique toxicological properties, are
usually but not always nonspecific or physical toxicants, can cause
narcosis, and can disrupt membranes physically and functionally. A
number of factors control the toxicity of surfactants to aquatic or-
ganisms, among them, ethoxylate chain length, the presence of esters
versus ethers, and hydrophilic-lipophilic balance (HLB). Rates of up-
take and penetration into an organism's tissues are highly dependent
on species (Abel, 1984; Wells, 1974~.
Acute toxicity data of some surfactants used in current formu-
lations (circa early 19SOs) are presented in Table 3-4 (WelIs et al.,
1985~. New and more effective formulations may have different sol-
vents and different combinations or types of surfactants. Toxicity
in Table 3-4 is expressed as a 1- or 2-day EC50 for two crustaceans,
Artemia sp. and Dc~phnia magna. Results of these laboratory tests
show that the anionic surfactants are generally more toxic than the
nonionic surfactants or esters, toxicities being influenced by alkyl
chain length, degree of dispersion, and HLB.
Studies on surfactants cover a wide range of organisms because
of concern for effects on membranes, reproductive stages, bacte-
ria, behavior (especially chemoreception), and other subtle sublethal
changes in exposed organisms (Abel, 1974; Moore et al., 1986~.
Solvents were the most toxic components of some early disper-
sants, due to high concentrations of aromatic hydrocarbons in the
petroleum fractions employed (Nelson-Smith, 1972; Smith, 1968~.
Several types of solvents are now used in most formulations (see
Chapter 2 and Appendix A), and they are far less toxic (Caneveri,
1986~. Nagell et al. (1974) and Weds et al. (1985) have shown tox-
icities to decrease in the order: aromatic hydrocarbon > saturated

100
USING OIL SPILL DISPERSANTS ON THE SEA
hydrocarbons > glycol ethers > alcohols. Third-generation concen-
trate dispersants tend to use less toxic solvents, such as glyco} ethers.
Acute Toxicity of Formulations
More than 100 studies have been conducted on acute lethal
toxicity of dispersants alone, more than half of them on currently
used second-generation dispersants (Doe and Weds, 1978; Doe et
al., 1978; Dye and Frydenborg, 1980; Nelson-Smith, 1972, 1980,
l9S5; Pastorak et al., 1985; Sprague et al., 1982; Wells, 1984~. Such
an extensive data base of varying quality invites periodic critical
analysis by dispersant, organism type and stage, and method of
exposure before definitive statements can be made about the acute
toxicity of any one formulation. This has been done for Corexit 9527
(Wells, 1984~.
Table 3-5 lists toxicity data, expressed as l.C50s for a wide va-
riety of species and dispersants. A wide range of values is reported,
including the following:
~ In Weds (1984) 4-day LCsos were 150 to greater than 10,000
ppm.
· Eleven dispersants tested with rainbow trout showed 4-day
Is of 260 to greater than 10,000 ppm (Doe and Wells, 1978~.
Early EPA data showed 2-day LC50s for Artemia sp. of 1.2
to 100,000 ppm for 15 products (Dye and Frydenborg, 1980~.
· In a study with freshwater phytoplankton and several dis-
persants, estimated 2-day LC50s were 1 to 575 ppm (Heldal et al.,
1978).
Studies by Kobayashi (1981) with sea urchin embryonic stages
gave threshold concentrations of 0.32 to 320 ppm.
i,
A range of 0.1 to 20,000 ppm for a wide range of species and
stages were compiled in Pastorak et al. (1985).
From Table 3-5 it can be seen that the "second-generation"
conventional dispersants, such as BPllOOX and Corex~t 7664, are
generally much less toxic than earlier formulations (BP1002, early
Finasol formulations).
One useful way to present dispersant toxicity data is by testing
several products on one species (Table 3-6). Table 3-6 illustrates that
the majority of products had l.C50s and EC50s greater than 100 ppm
to a planktonic crustacean, that is, a marine copepod.
Some formulations with high toxicities to certain species still
exist. Most research studies have examined only Corexit, BP, and

110
USING OIL SPILL DISPERSANTS ON THE SEA
above 100 ppm for exposures of 6 hr to 4 days. However, many more
reported toxicity thresholds are below 100 ppm, and some life stages
are extremely sensitive. A lO-m~n ECso for sea urchin sperm is 0.03
to 0.05 ppm, and is the only laboratory-derived threshold concentra-
tion so far that is likely to be still encountered-in the field hours after
dispersant use.
Patterns of sensitivity do not readily emerge. The threshold con-
centrations for eggs, embryos, and larvae are widely spread, showing
EC50 values from 0.0003 to 1,000 ppm. Crustaceans exhibit wide
ranges of toxic thresholds. Freshwater species appear to be less sen-
sitive than marine species.
For Corex~t 7664 (Table 3-8), Ladner and Hagstrom's (1975)
LC50s show that there may be increasing sensitivities from crus-
taceans to mollusks to fish, although there are exceptions. Seventy-
five percent of toxicity thresholds for this dispersant are above i,000
ppm. A similar evaluation for BP1IOOX shows the greater sensitivity
of some crustaceans, and approximately 80 percent of all reported
threshold concentrations for BPl1OOX are over 1,000 ppm. Table 3-9
compares the three dispersants in terms of the number of tests in each
concentration range. Although there is considerable overlap, Corexit
9527 is generally more toxic than the other two. Such evaluations
(Tables 3-7 to 3-9) could be usefully compiled for all extant disper-
sant formulations and local species of interest as an aid to on-scene
coordinators at spill sites (Trudel, private communication).
Factors Influencing Acute Toxicity
A number of physicochemical and biological factors influence
the toxicity of a dispersant formulation (Wells, 1984~. These fac-
tors are important to understand because estimates of toxicity are
relative not absolute numbers, and they change depending on en-
vironmental conditions and biological populations being exposed.
Physicochemical Factors
Surfactant molecular structure and ionic state were considered
by Portmann and Connor (1968), Bellan et al. (1969), George
(1971), Wildish (1972), Abe} (1974), Nagell et al. (1974), Macek and
Krzem~nski (1975), Tokuda (1977a,b), Tokuda and Arasaki (1977),
Wilson (1977), Ernst and Arditti (1980), and Wells et al. (1985~.
Solvent type and aromatic content were considered by Shelton
(1969), Nagell et al. (1974), I,adner and Hagstrom (1975), Wilson

TOXICOLOGICAL TESTING OF OIL DISPERSANTS
115
et al., 1974; Swedmark et al., 1971, 1973~. Other comparisons of
fishes, bivalves, and crustaceans were made by Macek and Krzeminski
(1975), Lonning and Falk-Petersen (1978), and Wells et al. (1982~.
Phylogeny
Phylogeny is an important factor. Dispersant ranking tests differ
with phyla (Abel, 1974; Beynon and Cowell, 1974; Boney, 1968;
Heldal et al., 1978; LaRoche et al., 1970; Wilson, 1974~. Foliose
lichens are more sensitive than crustose (Cullinane et al., 1975~.
Life History Stage
The influence of life history stage varies for different species.
Teleost fishes, despite their great commercial importance, have re-
ceived only limited study. For example, fish eggs are often very
susceptible to dispersant at time of fertilization. Developing em-
bryos are less sensitive than fish larvae (Linden, 1974; Wilson, 1976~.
Sensitivity of both embryos and larvae vary with dispersant formula-
tion (Linden, 1974; Lonning and Falk-Petersen, 1978~. For some fish
larvae, the difference in susceptibility between species is less than the
difference between different ages of a single species (Wilson, 1977~.
Young life stages of other organisms, such as echinoid sperm and
larvae, and some species, such as copepods, appear to be particularly
sensitive. Larval resistance of crustaceans increases with age, based
on studies with surfactants only (Czyzewska, 1976~. For polychaetes,
the most sensitive stages are gravid animals (Fores, 1975~. Other
studies considering life history include Portmann (1969), BeHan et
al. (1972), and Abel (1974~.
Physiological Factors
Physiological factors include seasonal variation in susceptibiity
to dispersants (Baker and Crapp, 1974; Braaten et al., 1972; Crapp,
1971a,b,c; Fingerman, 1980; Perkins et al., 1973~. Previous exposure
and acclimation makes a difference (Abel, 1974~. The transition
from yolk sac to feeding is especially susceptible (Lonning and Falk-
Petersen, 1978; Wilson, 1977~. Health and feeding state are also
important (McManus and Connell, 1972; Wilson, 1977~. Starvation
of fish larvae has been found to increase their susceptibility (Wilson,
1977~.

116
USING OIL SPILL DISPERSANTS ON THE SEA
Of ah the many possible factors, five have the primary influence
on toxicity thresholds, by ~ to 3 orders of magnitude when changed:
type of surfactant, type of solvent, water temperature, phylum, and
stage of development (WelIs, 1984~. Few studies varying these fac-
tors have been conducted in a single laboratory where each variable
can be controlled. Wilson's (1977) study with fish larvae was one; it
considered the influences of aromatic content of the solvents, temper-
ature, salinity, and species. Work with copepods and brine shrimp
(Wells et al., 1982; WeDs, unpublished data) has also shown the in-
fluences of temperature and species, toxicity thresholds increasing in
magnitude with declining temperatures.
The influence of these factors becomes apparent when evaluating
sets of data for any one dispersant (see Tables 3-S and 3-9~. Most
products produce wide threshold ranges, even the reportedly "low
toxicity" products such as Corex~t 7664. Relatively few products
approved for use in several countries fall into the range of high
acute toxicity (4-day LC50 less than 10 ppm). Products that do give
such high toxicities to local organisms should be used with caution,
especially in nearshore environments (Tables 3-5 and 3-6~.
Additional work on standardizing methods (WelIs, 1981; Wells et
al., 1984b) and on studying sublethal effects and their causes should
clarify the major influencing factors, the degree of their influence,
and the implications of such variable responses to the field effects of
dispersed oils.
Temperature Influence on Toxicity of Dispersants
A wide range of studies (Or~zie and Garofalo, 1981; Wells, 1984;
Wilson 1977) show that dispersants become less toxic with lowering
temperatures. This is most accurately shown by comparing threshold
concentrations at the different temperatures. This relationship holds
for Corexit 9257 which is, or has been, used as a reference dispersant
in many studies.
Wells reported 1-<lay I`C50s, median lethal concentrations, show-
ing an order of magnitude lower toxicity at 15°C (51 to 96 ppm
concentration) than at 25°C (greater than 560 ppm concentration)
with Artemaa sp. and Corexit 9257. For scallops, Or~zie and Garo-
falo (1981) found that as temperature increased, the concentration of
Forest 9527 required to kill 50 percent of the scallops decreased: 200
ppm at 20°C, 1,800 ppm at 10°C, and 2,500 ppm at 2°(~. They also
noted that dispersant concentrations that were not lethal to scallops

TOXICOLOGICAL TESTING OF OIL DISPERSANTS
117
during winter temperatures caused greater than 50 percent mortality
at summer temperatures.
The reasons for the higher toxicity at higher temperatures may
be a combination of increased uptake rates of chemicals, greater
exposure due to increased activity of the organisms in the water,
and combined factors such as higher temperatures and lower-oxygen
levels. The exact mechanisms for the higher toxicity have not been
elucidated.
In general, the same phenomena occurs with dispersed petroleum
oilsgenerally higher toxicities at higher temperatures in laboratory
exposures (Bobra and MacKay, 1984~. The implications of these
studies are that water temperature has a profound influence on the
toxicity of dispersants. There are significantly higher sensitivities of
organisms in warmer waters and in summer as compared to winter
conditions. Individual dispersants should be screened at the range of
expected environmental temperatures and threshold concentrations
reported that could be used by on-site commanders in decisions
regarding dispersant deployment.
Sites and Physiology of Toxic Action
Contact, uptake, internal storage, toxic action, detoxification,
and deputation are all processes by which a marine organism re-
sponds to and may be affected by dispersants. Thus, understanding
these processes within exposed organisms is crucial to understanding
why species sensitivities vary, which sublethal effects are significant,
and whether dispersant-oi} combinations might be more harmful than
either one by itself. It is also important to know whether toxicity is
temporary or permanent.
Few studies have used weD-characterized dispersants or known
constituents, hence much understanding is tentative or based on
detergent-surfactant literature. Early dispersant formulations-and
anionic and nonionic surfactants act "often physically and irre-
versibly, on the respiratory organs and other tissues of aquatic organ-
isms, and reversibly, depending upon exposure time, on their nervous
systems" (WelIs, 1984~.
A large number of studies describe the work of early investigators
on the sites and physiology of toxic action of dispersants, much of the
work being conducted at high concentrations in order to investigate
the various responses (WeDs, 1984~. Some constituents of dispersants
appear to cause disruptive effects to membranes and narcosis of the

118
USING OIL SPILL DISPERSANTS ON THE SEA
whole organism. No single action is implicated, but rather a total
response of the surface membranes and tissues, particularly gills, to
the exposure of surface-active agent. Behavioral responses include
cessation of feeding, slowed swimming, disorientation, impaired lo-
comotion, and paralysis often leading to death (if the exposures are
high and long enough). For example, fish gills were damaged under
200 ppm exposures to Oilsperse 43 over ~ to 4 days (McKeown and
March, 1978~. Blood enzyme (cathepsin D and acid phosphatase)
activities were increased in shrimp exposed to a high concentration
(10 to 100 ppm) of a nonionic detergent, Solo, for 72 hr. presum-
ably reflecting a change in the membrane permeability of lysosomal
enzymes (Drewa et al., 1977~. Asphyxiation due to the swelling of
gill lameliae and changes in membrane permeability is the princi-
pal manifestation of toxicity in fish (Granmo and Koliberg, 1976~.
Reduced surface tension may also play a role with HeLa cells (a spe-
cialized cell line used in bioassays) and nonionic surfactants (Ernst
and Arditti, 1980~. Certainly, "asphyxiation by surfactants packing
at gill surfaces appears to be one main physical toxic mechanism of
surfactants" (Pastorale et al., 1985), but evidence of the exact mech-
anisms and the NOEL (no-observable-effect level) concentrations are
not yet conclusive.
Surfactant molecules have both lipophilic and hydrophilic chem-
ical groups, and surfactants of different HLB characteristics are usu-
aDy blended in the solvents to ensure the separation of the of} droplets
when dispersed. Crustacean surfaces and gills, which are largely hy-
drophobic, tend to be contacted by low HLB surfactants and hydro-
carbons. Fish gills are coated with mucus and are less hydrophobic.
Such differences may help explain the different sensitivities of crus-
taceans and fish to water immiscible and water-miscible dispersants
(Nagell et al., 1974~. Considering the differences between the exter-
na] structure and composition of fish and crustaceans, the influence
of the molting cycle on water uptake and loss in crustaceans, and the
way by which ions and water are regulated or otherwise controlled in
many species, variations in sensitivity are not surprising.
Sublethal Effects
Many studies, performed mostly in the 1970s, have examined
sublethal effects. Sublethal responses such as reproduction, behav-
ior, growth, metabolism, and respiration usually occur at levels wed
below lethal thresholds, and hence are the most sensitive biological

TOXICOL O GICA L TESTING OF OIL DISPERSA NTS
Lethal
Thresholds
Sublethal
Thresholds
Expected Initial
Concentrations in
Water Column
119
1
1''''..;...-. .-,-,L, - ~ ~
,. .. ... ~~..~. ~..~..~., ~...~.~i~ ~~ ~~ ~!
L --my ~~ -~-i
1 1 1 1
10 1 10° 101 1o2 103 104
Concentration, ppm
FIGURE ~2 Comparison of lethal and sublethal threshold concentrations and ex-
pected concentrations in the water column for dispersants, as of 1982. Source: Adapted
from Wells (1984~.
responses. Normally, although not always, the laboratory exposure
durations are 1 to 4 days longer than organisms that would be ex-
posed in most dispersant use situations in open waters. Further,
laboratory exposure concentrations of reported sublethal effects nor-
maby are 1 or 2 orders of magnitude above highest anticipated con-
centrations in field use (see Figure 3-2~. Organisms from bacteria to
algae and invertebrates to fish exhibited varied biological responses
to dispersants in 50 to lOO sublethal laboratory studies (Wells, un-
published compilation; Nelson-Smith, 1985~. As with acute toxicity,
the range of threshold concentrations is extremely wide, from less
than 1 ppm to 106 (undiluted dispersant) based on exposures from
10 min to 3 weeks (Table 3-10~.
Some studies have described effects of dispersant applied di-
rectly to external surfaces or injected into organisms. This work
is particularly relevant to interpreting dispersant effects on inter-
tidal organisms, if dispersants are applied directly onto shorelines.
Limpets dropped off rock surfaces in response to dispersants (Black-
man et al., 1977~. However, Fingerman (1980) observed that the
regeneration of killifish caudal fins were unaffected when BP1OOOX
was injected in amounts of I:8O by weight for each fish.
The principal studies of sublethal effects of solvents have included
hydrocarbons (such as naphthalene) and mixtures (such as kerosene)
that contain them (Neff, 1979; Nelson-Smith, 1972; NRC, 1985~;
many responses have been measured. In contrast, few sublethal
studies have been conducted using other components known to be in
dispersant formulations.

122
USING OIL SPILL DISPERSANTS ON THE SEA
One example is Payne (1982) who showed that fish (Salmo gaird-
neri), crabs (Cancer irroratus), and mollusks (Ch.lamys islandicus)
"had the capacity for enzymatic hydrolysis of the complex fatty
acid ester mixtures found as surfactants in second-generation disper-
sants."
Laboratory and fieldwork comparing of} with dispersed of} has
tended to replace sublethal toxicity studies of dispersants alone, be-
cause it is believed that organisms under natural conditions would
be exposed only briefly to very low concentrations of dispersant.
However, this position requires examination for various marine habi-
tats and organisms, using recognized hazard assessment approaches
(Cairns et al., 1978~.
Hazard Assessment of D~spersant Alone
Effects due to the dispersant solvent and surfact ants in the water
column may be surmised only from laboratory studies, as field studies
have not examined this question. A commonly accepted approach for
laboratory and field comparisons and predictions does not yet exist.
Exposure in the water column depends on the concentration-time
profile of components as they dilute and degrade through various
processes, such as advection, volatilization, solubilization, diffusion,
bacterial degradation, uptake by organisms, and detoxification.
Normally, a portion of the dispersant applied to an of! slick
misses the of] and enters the water column directly, particularly if
dispersant droplets are large and slick thickness and distribution
varies (Chapters 2 and 5~. Dispersant may also partition from the
of] droplets into the water. This effect has been demonstrated by
laboratory toxicity experiments with Conceit 9527 and mineral oil
(Wells et al., 1982), and may be a common phenomenon (Fingas,
private communication).
The above dispersant concentrations that were measured are:
. range of less than 0.2 to 1.0 ppm (McAuliRe et al., 1975~;
· 1 to 10 ppm for a short period after application (Canevari
and I`indblom, 1976~; and
1984~.
up to 13 ppm at various depths and times (Bocard et al.,
Concentrations in the water for uniform mixing to various depths
and rates of application have been calculated:
· 1 to 12 ppm for shadow inshore areas (Griffiths et al., 1981~;

TOXICOLOGICAL TESTING OF OIL DISPERSANTS
123
· 1 ppm for 1,000 see in top 3 m (Mackay and Wells, 1983~; and
· 0.5 to 2.0 ppm in the top 2 m, after an application of 10 to
4() liters/ha (Mackay, private communication).
McAuliffe et al. (1981) calculated total dispersant exposure un-
der the best dispersed of} slick to be 3.2 ppm-hr in southern California
field tests (see Chapter 4~. This calculation is based on an integra-
tion of the dispersed of} concentrations measured over 12 hr. In
addition, it was assumed that the dispersant, which was sprayed at
a concentration of 5 percent that of oil, was distributed in the water,
as were the dispersed of! droplets. The above numbers are depen-
clent on application rates, depths, sampling, and chemical analysis
methods. The evidence is limited, but at presently recommended
application rates with elective dispersants, concentrations as high
as 10 ppm may be expected initially. In the open ocean, smaD-scale
field tests (see Chapter 4) have indicated that the concentration of
dispersant in water falls to less than ~ ppm within hours. Hence,
even initial concentrations in the water column are below most, but
not all, estimated lethal and sublethal concentrations (Figure 3-2)
derived from "constant" exposure experiments. These experiments
were conducted for a much longer period (24 to 96 fur). Therefore,
the effects on the field were expected to be much less.
Some effects of dispersants on organisms in the sea may occur,
considering the variety of organisms and biological processes in the
upper-water column, their frequent concentration at oceanic bound-
aries (surface microlayers and convergence zones caused by surface
currents, winds, and Langmuir circulation) and nutrient locations,
and the demonstrated sensitivity of some single organisms (partic-
ularly reproductive and larval stages). However, such effects would
probably be minor and short-lived due to dilution of materials and
recruitment of organisms from unaffected areas.
In conclusion, major effects (other than on insulation capability
of fur and feathers) should not occur in the near-surface waters due
to dispersant alone, provided properly screened dispersants are used
at recommended application rates.
TOXICITY OF DISPERSED OIL
This section addresses exposure assessment, comparative toxi-
city, and joint toxicity. Laboratory work is reviewed later in this
chapter; field studies, which assess both toxicological and ecological

124
USING OIL SPILL DISPERSANTS ON THE SEA
effects of dispersed oil, are described in Chapter 4. Case histories of
spiRs in which dispersants were used are reviewed in Appendix B.
The following discussions of marine ecotox~cology of chemically
dispersed oils are based on considerable literature on dispersants, oils,
and dispersed oils (e.g., Allen, 1984; Doe et al., 1978; Nelson-Smith,
1972, 1980, 1985; NRC, 1985; Sprague et al., 1982~.
Exposure Assessment
Exposure assessment involves estimating the concentrations of
tox~cants to which the organisms wid be exposed and the time of
exposure. This assessment is the first step in the process required to
estimate potential damage to marine organisms. Once the exposure
to toxic materials is known, it can be combined with laboratory mea-
sures of toxicity to obtain a hazard assessment. Exposure assessment
must take into account the several factors affecting of} concentration.
Untreated of} produces a certain level of exposure to surface or near-
surface organisms; treatment with chemical dispersants modifies this
exposure, moving the of} from the surface slick into the water col-
umn as droplets with a significant lifetime. Chemically dispersed of!
thus reaches a greater volume in which organisms can be affected,
but at the same time it is being diluted so that those effects will
be mitigated. Measured concentrations of of} in water reported at
test oil spills (Chapter 4) have frequently been regarded as repre-
sentative (McAuliffe et al., 1980, 1981; Nichols and Parker, 1985~.
When dispersants are used in confined areas with poor circulation,
concentrations of dispersed of} in the water column will be higher
than those found under open-water, experimental spills. In Chapter
4 recent field experiments designed to stimulate the latter situation
will be discussed.
Factors Affecting Comparative Toxicity
Some of the physicochemical and biological factors influencing
toxicity of dispersed oils and the magnitude of their effects are wed
known (Mackay and Wells, 1981; NRC, 1985; Sprague et al., 1982~.
Key biological factors to consider with chemically dispersed of] in-
clude phylum, life stage, physiological condition, and habitat. An
ideal theoretical structure for understanding the influence of these
factors would allow for
· extrapolation from one species or region to another;

TOXICOL O GICA L TESTING OF OIL DISPERSA NTS
125
· evaluation of joint toxicity of dispersant and of} in dispersions
prepared under different circumstances; and
· evaluation of the linkages between dispersant effectiveness
and toxicity of dispersant and dispersed oil.
The current limitations to fundamental understanding of such broad
relationships, due to the limited data base, somewhat restrict the
application of the laboratory-derived and field toxicity data bases
and their use in predicting possible sensitivities of species exposed to
dispersed oils under various field conditions.
Joint Toxicity
Joint toxicity, also referred to as joint action or mixture toxicity,
occurs where two or more chemicals are exerting their effects simul-
taneously. Although the terminology is not standardized and is often
used ambiguously, one mode! of joint toxicity describes the effects of
mixtures of chemicals as additive, more than additive (synergistic),
or less than additive (antagonistic) (Calamari and Alabaster, 1980;
Marking, 1985; Rand and Petrocelli, 1985; Sprague, 1970~. The
combined effect of dispersant and of} could be a simple combination
of effects each causes separately; but synergistic toxicity, which is
greater than the sum of the two separate exposures, is a possibility
that must be seriously considered.
As discussed earlier, joint toxicity cannot be assessed by a
straightforward comparison of of} toxicity with dispersed oil toxi-
city. In most experiments using of} alone, the of} remains primarily
at the surface of the experimental tank, and only a small fraction
the water-soluble fraction (WSF), which is sometimes called "water-
accommodated," a term including fine droplets as well as truly dis-
solved components dissolves or is dispersed in the water. When
dispersant is added, the limited volume of the experimental system
experiences a much higher concentration of dissolved plus dispersed
oil components. Even if the WSF is compared with the dispersed
oil, this situation exists. Thus, based on such exposures, many early
experiments concluded that dispersed of} was much more toxic than
oil alone.
In contrast, laboratory experiments comparing toxicity of the
WSF of of} with the WSF of dispersed oil, generally have found the
toxicity of the two indistinguishable.
This experience in accounting for the WSF suggests that mean-
ingful evolution of joint toxicity must involve adequate chemical

126
USING OIL SPILL DISPERSANTS ON THE SEA
analysis of the of} in the water phase to allow comparisons of hydro-
carbon toxicity on the same hydrocarbon scale, whether dispersants
are present or not. This observation also reinforces the need for
thorough, comprehensive experimental design in any experiments
examining the toxicity of hydrocarbon versus hydrocarbon plus dis-
persant (Wells et al., 1984b).
Questions also arise concerning the most appropriate experi-
mental procedures for studying dispersed oils, such as constant ex-
posures versus declining concentrations. Simple, measurable toxicity
parameters in individual organisms are needed to predict effects on
population success (i.e., survival of individuals, reproduction and
development, and recruitment).
Dispersant composition influences toxicity directly and also indi-
rectly because a more effective dispersant mobilizes more oil into the
water column (Mackay and Mascarenhas, 1979; Mackay and Wells,
1983; Nes and NorIand, 1983; Wells, 1984; Weds et al., 1984a). This
relationship must be considered in an accurate assessment of joint
toxicity.
LABORATORY STUDIES WITH DISPERSED OIL
Since the Torrey Canyon spill in 1967, many studies of the effects
of dispersed oils on marine organisms under laboratory conditions
have measured toxicities and relative toxicities of various oils, of!
with dispersants, and dispersants themselves. This section reviews
studies employing dispersed of} or oil-dispersant mixtures on a wide
range of organisms from phytoplankton to fish.
To evaluate hazards to marine organisms caused by dispersant
use, the most important toxicity information needed is the compari-
son of chemically dispersed oil (particularly the effects of dispersant
at concentrations normally used) with undispersed or physically dis-
persed oil, under conditions approximating those in the field. As
discussed previously, the most appropriate laboratory measurement
is the toxicity of the water-soluble fraction of of! or dispersed oil.
Unfortunately, about two-thirds of the literature published prior
to 1987 does not give values for of! concentration in the water phase,
but instead uses the total of! per unit volume, or nominal con-
centration. Approximately one-third of the many tests measured
the dissolved hydrocarbons that cause immediate biological toxicity.
As noted earlier, in systems where of} or dispersant forms a sepa-
rate (floating layer) phase, basing toxicity on nominal concentrations

TOXICOLOGICAL TESTING OF OIL DISPERSANTS
127
leads to unrealistically high LC50 or EC50 values (i.e. underestimates
of toxicity). A major portion of the toxic fraction remains in the
floating layer and does not reach the test organism, resulting in
erroneous estimates of exposure concentrations and toxicities.
If physically dispersed of} (where most of the of} resides in the
surface layer) is compared with chemically dispersed of} (where much
of the oil is accommodated in the water) using nominal concentra-
tions, the chemically dispersed of} appears to have a higher toxicity.
For example, based on studies using nominal concentrations, it has
been hypothesized that under natural field conditions, toxicity of
oil-dispersant mixtures to organisms would be greater than that of
untreated of! (Nelson-Sm~th, 1972; Swedmark et al., 1973~. As wiD
be shown in the following sections, tests in which water-soluble frac-
tions and water-accommodated fractions are measured and used as
a basis for toxicity generally show no difference between physically
dispersed and chemically dispersed oil.
As stated above, approximately one-third of the studies, varying
with organism grouping, reviewed for this report measured the water-
soluble fraction. Many studies used much higher concentrations of
of} and dispersant than would likely be found under field conditions,
except in highly enclosed bodies of water where the volume of of! may
be large relative to the receiving waters. Some studies compared the
toxicity of dispersed of} to dispersant alone, but not to of} alone. It
is, therefore, difficult to estimate threshold concentrations accurately
from these studies, and hence address the joint toxicity of dispersed
oil.
Swedmark et al. (1973) and Doe and Weds (1978) proposed
that the primary difference between untreated of} and dispersed oil
under laboratory conditions was "that effective dispersants simply
make more oil or its many components available to aquatic organ-
isms," rather than causing greater-than-additive effects. Norton et
al. (1978) likewise correlated the "coarsening [formation of larger
particles] of the dispersion to a reduction in toxicity," that is, less of!
was then available to the organisms.
Bobra et al. (1979) recognized the importance of separating the
contributions of dissolved hydrocarbons, dispersed of} particles, and
dispersants in the laboratory to identify which effect dominates tox~-
city based on the fate of materials under different aquatic conditions.
This information was then incorporated into a hazard assessment
of dispersed oil. Bobra et al. (1979, 1984) and Mackay and Weds
(1983) have attempted to mode} these contributions of dispersant,

128
USING OIL SPILL DISPERSANTS ON THE SEA
dissolved oil, and particulate of} to acute toxicity at different oil-
water ratios and volumes and at different weathering states, using
crustacea as model organisms and standardized physicochemical and
toxicity data for the remaining input. For example, when a fresh
Norman Wells crude of} is dispersed with Corexit 9527, 85 percent
of the toxicity (to DapEnia magna) was attributed to the dissolved
hydrocarbon fraction, 14 percent to the suspended particles, and less
than 1 percent to the dispersant. A similar system, but with the oil
weathered by 42 percent, gave 87 percent of the toxicity in particles,
10 percent in the dissolved fraction, and 2 percent in the dispersant
(Bobra and Mackay, 1984; Bobra et al., 1984~. This kind of model
is useful for assessing the sources of toxicity in of} dispersions to
different organisms over the crucial time periods after a major spill.
It has been hypothesized that acute toxicity of chemically dis-
persed oils fans between that of the whole of] and its water-soluble
fraction (Figure 3-3; Weds, 1985; Mackay and WeDs, unpublished
data). The exact location of the toxicity curve for each of! dispersion
is determined uniquely by each laboratory or field spill situation, as
wed as the chemical components.
Mackay and Wells (1980, 1981, 1983) and Weds et al. (1984a,b)
described the many factors known to influence the toxicity of dis-
persed oils (compare with discussion entitled "Factors Influencing
Acute Toxicity," earlier in this chapter). These include
time.
the stability of the hydrocarbon mixture;
the ratio of dissolved to particulate oil; and
changes in concentration and composition of of} over exposure
Whether toxicity may be synergistically enhanced that is, or-
ganisms will experience greater effects from hydrocarbons and disper-
sant surfactants together than would be predicted from experiments
with either alone is a more difficult hypothesis to test because it
involves eliminating the large effects of individual components. Only
a few investigators have seriously attempted to investigate this prob-
lem. One attempt was a detailed study of fish responses to dispersant,
oil, and dispersed of] that included hydrocarbon measurements in the
water (Weds and Harris, 1980~. They concluded that the interaction
of dispersant and of! was additive, and that "with an effective but
low-tox~city dispersant, the acute toxicity of the chemically dispersed
of! reflected primarily the toxicity of the oil-derived hydrocarbons."
This study and others discussed below (e.g., PeakaB et al., 1987)

TOXICOLOGICAL TESTING OF OIL DISPERSANTS
100
10
\
l WATER-
SOLUBLE
FRACTION OF
\ FRESH
\ CHEMICAL \
· DISPERSION ~
\ OF FRESH CRUDE \
.
PHYSICAL
DISPERSION
\ OF FRESH CRUDE
Exact location
_ dependent on
~ effectiveness,
\ toxicity, and
other factors
.
.
.
-
1 1 , , ,
0.1 1.0 10 100
INITIAL CONCENTRATION OF EXTRACTABLE ORGANICS, ppm
FIGURE ~3 Hypothetical relationship of the toxicity curares for water-soluble frac-
tions (WSF), chemical dispersions, Ed physical dispersions of fresh crude oils. Concen-
trations are of extractable organ measured by gas chromatography or fluorescence.
Numbers on axes represent approximate Clues for manne planktorac crustaceans.
Curves would be three-dimensional in practice. This figure formed part of the overall
hypothesis tested in the study on the relationship between the effectiveness of disper-
sants and the toxicity of dispersants Ed disposed oils (see Mackay and Wells, 1983~.
Source: Wells, 1985.
show that the apparently greater toxicity of chemically dispersed of}
is generally a reflection of exposure, not a reflection of a greater
inherent toxicity.
The following discussion is devoted to a detailed survey of the
current literature covering phytoplankton, marine plants, zooplank-
ton, crustaceans, and other marine organisms. This literature has
not been recently reviewed (the last reviews were by Nelson-Smith,
1973; Sprague et al., 1982; and Pastorak et al., 1985~. Moreim-
portant, a substantial portion of the studies have misinterpreted the
toxicity of the dispersed of} because they used nominal concentrations

130
USING OIL SPILL DISPERSANTS ON THE SEA
rather than measured ones. Even though their numerical values for
threshold concentrations are incorrect, their observations on type,
duration, and recovery of responses are useful in understanding the
toxicity of dispersed of] and have been noted, where relevant, in the
following discussion.
Phytoplankton
Laboratory studies of the toxicity of dispersed of! to phytoplank-
ton are summarized in Table 3-11. Four of the seven studies (Chan
and Chin, 1985; Hsaio et al., 1978; Lacaze and ViDedon de Naide,
1976; ViDedon de Naide, 1979) report that dispersed of} is more
toxic than undispersed oil. However, these studies were incorrectly
based on the use of nominal of} concentrations and are not considered
further.
One investigator (Trudel, 1978) analyzed of} concentrations in
water by infrared spectroscopy, and measured response by carbon
fixation. His dose-response relationship was the same in oil and i:1
oil-dispersant mixtures, and no change occurred in toxicity of the
dispersed of} with the dispersant present.
Another study (Fabregas et al., 1984) measured the water soluble
fraction of weathered crude from the wreck of the tanker Urquiola,
and concluded that the toxicity of the dispersed of} was the same as
that of the dispersant (Seaklin 101-NT).
There were other observations as well. An increase in light
intensity increased the toxicity of dispersed Kuwait crude of! to phy-
toplankton. In the presence of Corexit 8666, toxicity increased by a
factor of 5 in darkness and increased by a factor of 9 in light (Lacaze
and ViBedon de Naide, 1976~. The weathered of} mixture, when il-
Juminated and mixed with dispersant (1:~), was the most toxic. In
another study, growth of the marine diatom Skeletonema costatum,
under the influence of dispersed oil, was the same as for of! alone, but
greater than that for dispersant alone (Tokuda, 1979~. Both studies
demonstrated similar toxicities of of] and chemically dispersed of} to
phytoplankton.
Macroscopic Algae and Vascular Plants
As with phytoplankton, three of the five papers reviewed on
macroscopic plants (Table 3-11) employ nominal concentrations and
conclude, without convincing evidence, that dispersant-oi] mixtures
are more toxic than of] alone (Ganning and Billing, 1974; Hsiao et
al., 1978; Thelin, 1981~.

TOXICOL OGICA L TESTING OF OIL DISPERSA NTS
131
The other two studies (the last two entries in Table 3-11) em-
ployed gas chromatographic analysis of the water-soluble fraction;
they consider seagrasses, which are discussed in Chapter 4.
Zooplankton
This section covers ad groupings that have been studied except
crustacea, which are discussed later.
Protozoa
Little work has been conducted with protozoa and dispersed
oils. Goldacre (1968) was the first to describe the narcotic effects of
hydrocarbons and some nonionic dispersants on the cell membrane
of amoebae, but no oil-dispersant mixtures were evaluated.
Rogerson and Berger (1981) determined the toxicity of oil-
dispersant mixtures to ciliates, Tetrakymena pyriformis and Colpid-
ium campylum, on the basis of growth rate. Corexit 9527 concentra-
tions above ~ ppm (nominal) were acutely toxic. The protozoa grew
better in dispersed oil tests than in of} alone. This was attributed to
the more rapid volatilization of the more toxic, aromatic fraction of
the of} from the dispersed of] mixtures. After of} had weathered, the
dispersant was apparently the primary toxicant.
Polychaetes
Polychaetes are known to be tolerant of of} and are often the first
species to colonize the benthic community after aIt of} spill (NRC,
1985~. The acute toxicity (l-day LC50s) of Corexit 7664 to Spionid
larvae was 889 ppm for the dispersant and 222 ppm for an Traq
crude oil-dispersant mixture (Latiff, 1969~. Likewise, 48-hr LC50s
for Corexit 7664 with the polychaete Ophryotrocha were extremely
high: 35,000 ppm for males, 30,000 ppm for females, and 12,000
ppm for larvae (\kesson, 1975~. With of} (not described) in a ratio
1:2, the toxicities became 580, 420, and 420 ppm, respectively. Even
though the data from these experiments were analyzed using nominal
concentrations, McKesson concluded correctly that the oil-dispersant
mixture was more toxic than the dispersant alone.
Mollusca
The only reported study on molluskan plankton deals with the
gametes, embryos, and larvae of two oysters (`Crassostrea anguiata

134
USING OIL SPILL DISPERSANTS ON THE SEA
and C. gigas) and the mussel Mytilus galloprovincialis (Renzoni,
1973~. Only very high nominal concentrations of hydrocarbons in
water, with and without dispersants, were toxic, producing responses
with the eggs and embryos. Oil-dispersant mixtures (1 to 1,000
ppm) were toxic to fertilization. The toxicity of oil and oil-dispersant
mixtures at high concentrations were similar, although the analytical
method using nominal concentrations is incorrect.
Echinoderms
A number of studies have been conducted exposing sea urchin
eggs, embryos, and larvae to oil-dispersant mixtures (Falk-Petersen,
1979; Falk-Petersen and Lonning, 1984; Lonning ~~d Hagstrom,
1975, 1976), but their conclusions have been brought into question
because toxicities were based on nominal concentrations and the
water-soluble fraction of the of} was not analyzed. Experiments were
conducted with Kuwait and Ekofisk crudes, a range of dispersants,
especially Cored 9527, and a number of sensitive sublethal embry-
ological responses.
Ichthyoplankton
The high commercial value of fish, combined with the vuinerabil-
ity of early life stages to oil, makes the toxicology with ichthyoplank-
ton particularly important. Unfortunately, only one paper compares
the toxicity of the water-soluble fraction of physically dispersed oil
and chemically dispersed oil. That study found chemically dispersed
of] less toxic than of} alone (Borseth et al., 1986~. In other studies,
nominal concentrations were used and, as expected, chemically dis-
persed of} was reported to be more toxic. Six of these papers are
compared in Table 3-12.
{ran crude of} (1,000 ppm nominal concentration) and Corex~t
7664 (100 ppm) produced narcosis or lethality in 1-day-old herring
larvae (Kuhubold, 1972~. After 2 days in static laboratory conditions,
the physically dispersed of! had lost its toxicity, but the chemically
dispersed of} had retained or increased its toxicity.
Another early study considered the effects of Russian crude oil
and dispersants on the eggs and larvae of northern pike, Eso~ lu-
cius (Hakkila and Niemi, 1973~. The study's main finding was a
description of the comparative sensitivities of the life stages to of]
dispersions. More than 60 ppm of} plus dispersant caused some egg

TOXICOLOGICAL TESTING OF OIL DISPERSANTS
135
mortality and 300 ppm caused complete mortality; this is high com-
pared to other results. Larval tests gave 2-day LC50s of 66 ppm
(stage IT) and 4.4 ppm (stage IlI). The toxicity of the oil-dispersant
mixture was greater than the oil, but the same as the dispersant
alone; and was attributed to the dispersant since it was a nonionic
surfactant in an aromatic solvent.
Linden (1975, 1976) studied the effects of Venezuelan crude plus
dispersant (BPllOOX, Finasol SC, and Finasol OSR-2) on the on-
togenetic development (i.e., embryonic movement and heart rates,
morphology, and length of larvae) of the Baltic herring, Clupea
harengus. Both acute and sublethal effects of the oil increased 2
to 3 orders of magnitude if the oils were dispersed by the least toxic
dispersant (BP1lOOX), and 3 to 4 orders of magnitude with a highly
toxic dispersant formulation, such as Finasol SC.
Two studies of oil-dispersant mixtures were conducted by Mori
et al. (1983, 1984~. They found that the tolerance of common sea
bass eggs is greater than those of parrotfish and flounder (Mori et al.,
1983), and that oil-dispersant mixtures were more toxic than oil alone
for the young of sea bream and Japanese flounder and the larvae of
stone flounder (Mori et al., 1984~. The results of these experiments
are questionable because the water-soluble fraction of the oil was not
measured, and toxicities were based on nominal concentrations.
Borseth et al. (1986) conducted a comparison of in viva and
in situ exposure of plaice (~leuronectes platessa) eggs to the water-
soluble fraction of Stati3ord A + B crude oil topped at 150°C and
mixtures with Finasol OSR-5. To cause significant mortalities (98
percent) required the fud strength WSF of the oil-dispersant mixture.
In contrast, 10 percent mortality occurred with the maximum WSF
concentration for the topped crude. At 1:1 dilutions of both WSFs,
mortalities were equivalent.
In spite of these experimental studies, a dependable generalized
hazard assessment with ichthyoplankton, and therefore to fisheries
potential, cannot be made without considerably more research.
Crustaceans
More work with dispersed oil has been conducted on crustaceans
than any other type of organism, due to their ecological and com-
mercial importance and the relative ease with which many species
can be studied. The sensitivity of many crustaceans, particularly
in young and molting stages, to dissolved and physically dispersed

138
USING OIL SPILL DISPERSANTS ON THE SEA
hydrocarbons as well as to dispersant formulations has been wed
documented (NRC, 1985; Sprague et al., l982~. A number of studies
are compared in Table 3-13, and additional details are given in the
text.
Copepoda
Lipid metabolism, swimming behavior, respiration, and survival
of the copepods Acartia sp. and Cyclops sp. were used as indicators
of toxicity in the early work of GyIlenberg and Lun~quist (1976~. A
number of potential sublethal ejects were identified with the disper-
sal of oil by Finaso! OSR-2 and Finaso} SC, but comparisons were
not reliable because only nominal concentrations were used.
Venezia and Fossato (1977) studied the acute and chronic effects
of suspensions of Kuwait crude oil and Corex~t 7664 on Harpacticoid
copepods, Tisbe ~oulbaselosa. They prepared aqueous phases of dis-
persant and of! (1:5), which they analyzed by gas chromatography
and fluorometry. Noting that the hydrocarbon concentration in the
aqueous phase depends mainly on the amount of dispersant present,
and less on the quantity of of! added, they rejected the hypothesis of a
synergistic effect of hydrocarbons with this dispersant, assigning the
effects to the higher of} concentrations in the oil-dispersant suspen-
sion. Even though the acute toxicity of the separated aqueous (~:5)
phase of the dispersant and of} mixture was 37 ppm (9-day LCso) and
9 ppm (20-day I`C50), exposure of the developing eggs and nauplii of
the copepods to 39 to 45 ppm (or lower) of this mixture showed no
significant effects on numbers of eggs or nauplii, or percent hatching.
Spooner and Corkett (1974) studied the effects of Kuwait 250°C
residue of} combined with BPllOOX on the feeding rate of Calanus
heigolandicus females. Toxicities were similar between of! and dis-
persed oil. Exposure to 10 ppm total of] (analyzed spectroscopically)
plus 2 ppm dispersant for 20 hr reduced the number of fecal pellets
produced, whereas 2 ppm of] and 0.4 ppm dispersant had no ef-
fect. Feeding rates recovered in Al treatments. Spooner and Corkett
(1979) found clear effects of of] on four species of copepods at 10
ppm.
Wells et al. (1982) studied the mortality of Calanoid copepods
(predominantly Pseudocalanus minutes with some Acartia hudson-
ica) in a white, low-toxicity, paraffinic mineral of! (MarcoT 70) with
Corexit 9527. Temporary Toss of the toxic components of the disper-
sant into the of} was shown by mixing the oil and dispersant together

TOXICOLOGICAL TESTING OF OIL DISPERSANTS
139
at different speeds and testing their aqueous dispersions. When mix-
ing stopped, the dispersant components, which had been dissolved
in the oil or associated with the interface, eventually partitioned
back into the water. The experiment demonstrated that dispersant
could stay in the of} phase and not the water phase with mixing as
done in the laboratory. Therefore, an incorrect conclusion may have
been made about dispersant concentrations in oil-water-dispersant
mixture dilutions in many bioassays, unless the experiments were
conducted during continuous mixing of all materials.
Foy (1982) demonstrated that 96-hr I.C50s for Calanus hyper-
boreus, when based on hydrocarbon concentrations measured by flu-
orescence spectroscopy, were lower in Pru~hoe Bay crude oil-water
mixtures than in oil-Corexit 9527 mixtures, that is, 73 (51 to 103)
ppm versus 196 (161 to 238) ppm, respectively. There was no evi-
dence that oil dispersal with the dispersant led to a dispersion more
toxic to copepods. The copepods were quite resistant to the Pru~hoe
Bay crude but suffered fouling with of] that may reduce survival in
similar exposures under natural conditions.
Falk-Petersen et al. (1983) studied the effects of of} and disper-
sants on plankton. And in 1984, Falk-Petersen and Lonning (1984)
summarized their many studies of the effects of oils and dispersants
on embryos and larvae of sea urchins and fish, and copepods. The
main finding of this body of work is that the fertilization and em-
brionic development of organisms may be affected by exposures at
quite low concentrations, but this requires confirmation with chemi-
cal analysis. Their studies also demonstrated the changes in toxicity
thresholds with organism and life stages.
Decapoda
Franklin and Lloyd (1986) used the standard U.K. Ministry of
Agriculture, Fisheries, and Food (MAFF) Crangon crangon (brown
shrimp) dispersant "sea test" to examine the relationship between of}
droplet size and the acute toxicity of oil-dispersant mixtures with the
use of a Coulter Counter. Toxicity increased with decreasing droplet
size. The authors speculated that with a distribution of very small
droplets, soluble toxic components were more rapidly transferred into
aqueous solution.
Anderson et al. (1980, 1981, 1984, 1987) and Anderson (1986)
have reported on the toxicity of dispersed and undispersed crude

144
USING OIL SPILL DISPERSANTS ON THE SEA
(10 percent solution), and mixtures (I) were tested. All treatments
caused increases in cardiac activity and oxygen consumption and dis-
ruption of feeding behavior, but effects were reversible. Conclusions
on comparative effects of of} and dispersed of} can only be considered
as tentative because of the use of nominal concentrations.
Ahsanuliah et al. (1982) described the acute lethal responses of
the crab Paragrapsus quadridentatus to Kuwait light crude, an Aus-
traiian dispersant (BP/AB), and an oil-dispersant mixture. Based on
of} concentrations measured by hexane extraction, 4-day LCsos were
63 to 70 and 69 to 106 ppm for the of} and oil-dispersant mixture,
indicating no significant difference in acute toxicity.
Capuzzo and Lancaster (1982) studied the physiological effects
of physically dispersed and chemically dispersed Southern Louisiana
crude of] and ingestion of an oil-contaminated food source on larvae
of lobsters, Homarus americanus. No enhanced toxicity was observed
due to the presence of dispersant, but the sublethal effects occurred at
concentrations expected in the water column during the first hours
or days of a major spill. Larvae were exposed to dispersions in a
continuous-flow system at 20°C for 4 days. Physically dispersed of}
had droplet sizes of 20 to 50 am (0.25 ppm) and chemically dispersed
of} (Corexit 9527) had sizes of 10 to 20 am (0.025 ppm). Concen-
trations were unusually low for this type of study and designed to
resemble the exposure expected in the water column during the first
days after a major spin. Survival of larvae was the same in aD treat-
ments (i.e., oil, of] plus dispersant, and controls). Exposure reduced
metabolism, as shown by lowered respiration rates and reduced ra-
tios of oxygen consumed to ammonia and nitrogen excreted. This
was interpreted to be a result of increased dependence on protein
catabolism, inhibited lipid utilization, and delayed molting. Larvae
did not accumulate of! droplets in their digestive tracts, but those
exposed to of} and dispersed of} had reduced metabolism during the
exposure. Lobsters exposed to oil-contaminated food also showed
reduced respiration.
Other Crustaceans
Percy (1977) reported on the effects of sublethal exposures to
dispersed oils on the respiratory metabolism of an arctic marine
amphipod, Onisimus (Boekisimus) Alibis. The relative magnitude
of the change in respiration rate was less in oil-dispersant mixtures

TOXICOLOGICAL TESTING OF OIL DISPERSANTS
145
than in oil alone, but in both cases, reversal of respiratory depres-
sion was influenced by of} type. Low concentrations (13 to 21 ppm
initial measured concentration) significantly depressed respiration
rates, whereas increased hydrocarbon concentrations (268 to 800
ppm initial measured concentration) reversed depression, and respi-
ration rates reached and even exceeded the controls (Wells and Percy,
1985~.
Duval et al. (1980, 1982) studied the lethal and sublethal physi-
ological and behavioral effects of physically and chem~caLy (Corex~t
9527) dispersed of} on the estuarine isopod Gnorimosphaeroma ore-
goner~sis under computerized flow-through exposure to the water-
soluble fraction. The extent of responses was greater in oil-dispersant
mixtures, even at lower total oil concentrations. The organisms re-
covered in clean water. Corex~t itself had a low toxicity (no mortality
in 4 days at 1,000 ppm). The 48-hr LC50 for of} dispersant was 32
(13-78 c.~.*) ppm, compared to 70 (2~203 cat.) ppm for physically
dispersed oil, suggesting slightly more toxicity in the chemically dis-
persed oil. The toxicity curves are linear but nonparallel, suggesting
that the mode of toxic action might be different in the two dispersion
types. The sublethal studies (Duval et al., 1982) showed that oil
alone gave patterns of sublethal responses as G. oregonensis similar
to of} plus dispersant: respiration rates, carbon assimilation rates
and efficiencies, naphthalene uptake, behavior (coordinated motor
ability), molting, and reproduction (frequency of mating).
Mackay and Mascarenhas (1979), Bobra et al. (1979), and
Mackay and WeDs (1983) discussed the need to develop a mathe-
matical analytical framework for expressing individual and combined
toxicities of dispersant constituents and dispersed oil. A formula was
developed to examine data for Daphnia sp., Artemia sp., and cope-
pods (Abernathy et al., 1986; Bobra et al., 1984~. This work wiD
result in a computerized joint toxicity mode} for the mixture that
takes into account dispersant, dispersant components, water-soluble
fraction of the oil, specific hydrocarbons, and of} droplets or particles
(Bobra et al., 1987; Wells, 1985; Mackay, private communication).
Mackay and Wells (1980, 1981) reported the effects of of} disper-
sions, water-soluble fractions, Corexit 9527, and chemically dispersed
of] on Artemia nauplii in static exposures at 20°C. In the chemical
dispersion, most of the of} was in particle (droplet) form, the stabil-
ity of the dispersion was greater, and the water-soluble of! fraction
*Range of 95 percent confidence limits.

146
USING OIL SPILL DISPERSANTS ON THE SEA
was more concentrated (shown by gas chromatography). At the
toxic threshold for the dispersion, the dispersant itself was at its
lethal threshold (2-day I'C50s were 24 to 45 ppm; Wells and Mackay,
unpublished data). Oil physically dispersed, settled, and diluted pro-
duced few effects in Artemia at 100 percent dispersion: 2-day LC50s
were greater than 41 to 65 ppm, based on concentrations of water-
accommodated of} (by fluorescence and gas chromatography) at time
zero hour. Chemically dispersed oil, prepared in a similar manner (18
to 24 percent dispersion), was similarly toxic: 2-day LC50s were 82
to 120 ppm of} (plus 37 to 55 ppm dispersant, since the dispersant-oi}
ratio was 1:2.5~.
In another experiment with dispersed fresh and weathered Lago
Media crude and Artemia (Mackay and Wells, 1980, 1981), 50 percent
mortalities were reached within 3 days in dispersions of 2.9 to 7.6 ppm
(measured by fluorescence) or 1.0 to 2.1 ppm (gas chromatography).
There were few differences between fresh and weathered dispersions.
Acute toxicities decreased as the dispersant-oi} ratio decreased from
1:10 to 1:50, confirming that the dispersant could contribute to acute
toxicity.
Mollusks
Pelecypod and gastropod mollusks, with many species in the
littoral and shallow sublittoral zones, are particularly susceptible to
oiling. At least nine laboratory studies (Table 3-14) show the ranges
of species, oils, and dispersants and responses evaluated in studies to
determine if dispersants change oil or oil component toxicity. With
bivalves, studies with measured concentrations showed equivalent
toxicities or lowered toxicities between the dispersed oil and the oil (or
its WSF) alone. Studies with nominal concentrations showed greater
toxicities for the mixtures, but such conclusions are suspect because
exposures were unknown for ah compared treatments. Physiological,
behavioral, and recovery experiments predominated with the bivalve
research and illustrate differential sensitivities and often the capacity
to recover from exposures.
For gastropods (Table 3-14), all studies used nominal concentra-
tions, thus invalidating conclusions about the comparative effects of
dispersed oils to oil alone, but showed that respiratory and behavioral
responses were quite sensitive to oil or dispersant exposures.
In summary, laboratory research on mollusks shovers that high
concentrations of dispersed oils can be toxic, but that little defensible

TOXICOLOGICAL TESTING OF OIL DISPERSANTS
147
evidence (with measured concentrations) exists to suggest higher
toxicities of oils and their components in the presence of dispersants.
Comparison of Laboratory Studies and Field Studies With
Measured Hydrocarbons
This section reviews and compares laboratory bioassays that
measured dissolved hydrocarbons ACE to Clot in the water-soluble
fraction from untreated and chemically dispersed crude oils with
those measured in the field, and it also compares the Cal to CIO
hydrocarbon fraction bioassays or behavioral studies of untreated
crude of} with dispersed of} bioassays using the same organisms.
Oil toxicity to organisms is thought to result principally from
hydrocarbons that dissolve into water from crude oils or refined
products (NRC, 1985~. A large number of laboratory bioassays have
been conducted with the WSF obtained by equilibrating of} and
water, but many have not measured these dissolved hydrocarbons.
Table 3-15 summarizes exposures to untreated of} and chemically
treated of! of several fish and a crustacean, expressed as ppm-hr, and
lists the salient laboratory studies that measured dissolved or added
hydrocarbon components to determine their effect on fish. This table
shows the 96-hr LCso values and the exposures (in ppm-hr) required
to cause 50 percent mortality among several Alaskan species. Most
of the species survived in the maximum possible concentration of
dissolved hydrocarbons from Cook Inlet crude oil; a condition that
never occurs in marine spills.
The largest number of studies with various species that measured
aromatic or tote] dissolved hydrocarbons in exposure waters was
reviewed by McAuliffe (1986, 1987a). The most extensive studies
were conducted by Rice et al. (1979, 1981), using subarctic species
in southern Alaska.
Rice et al. (1981) also determined the 96-hr LCso for the larvae
of five marine species to tote] aromatic hydrocarbons in the bal-
last water treatment effluent at Port Valdez, Alaska. The relative
proportions of the dissolved aromatic hydrocarbons in the effluent
discharge were very similar to those measured for water equilibrated
with Cook Inlet and Pru~hoe Bay crude oils. As for the studies
reported in Table 3-15, saturate hydrocarbons present in the ballast
water effluent were not measured.
McAuTiffe et al. (1981) compared exposures with those found
in the best chemically dispersed oil plumes of the 1979 California

152
USING OIL SPILL DISPERSANTS ON THE SEA
tests, and with exposures measured under untreated Pru~hoe Bay
crude oil slicks. The total of C1 to C,0 dissolved hydrocarbons under
untreated slicks were reported to be 1 ppm or less (McAuliffe et
al., 1981~. In later publications McAuliffe (1986, 1987a) quoted an
average integrated exposure of 0.002 ppm-hr, as listed in Table 3-15.
In other field observations, including those at oil spills, concen-
trations were as much as 100 times higher (Howarth, 1987; NRC,
1985~.
On the other hand, the relatively unpolluted area of Georges
Bank was sampled at 20 stations four times during 1977 (Farrington
and Boehm, 1987~. The concentration of dissolved hydrocarbons in
the water column ranged as follows:
February 14 to 60,ug/liter (ppb);
· May 1 to 25 ~g/liter (ppb);
August less than 1 to 5 ~g/liter (ppb); and
November less than 0.2 to 2 ~g/liter (ppb).
The February values were high because of the Argo Merchant oil
spin in December 1976 and January 1977. Over a 24-hr period, these
data give exposures of 0.005 to I.4 ppm-hr. If only the latter part of
the year is considered, the range is 0.005 to 0.12.
Under the best dispersed oil plumes of the 1979 California tests
(McAuliffe et al., 1981), the dissolved hydrocarbon concentration
was taken to be 150 ppb for the first 30 min (although samples as
high as 54 ppm were reported from 1 m depth 15 mitt after spraying,
more typical samples were ~ ppm) and because the concentration
decreased as a result of evaporation and dilution, the integrated
exposure over 24 hr is listed in Table 3-15 as 0.06 ppm-hr. Nevissi
et al. (1987) and McAuliffe (1987a) determined the exposures to
dissolved hydrocarbons required to cause 50 percent mortality of
chum salmon fry with untreated and chemically dispersed Pru~hoe
Bay crude oil. The total Cat to Cal o hydrocarbon content of the water
was measured ~ times during the 24-hr exposures.
University of Washington researchers (Brannon et al., 1986;
Nakatani et al., 1983, 1985) measured the effects of untreated and
chemically dispersed Prudhoe Bay crude oil on the homing of adult
chinook salmon (Oncorhynchus tshawylscha) in fresh water, adult
coho salmon (O. kisutch) in seawater, and the amounts of these oils
to cause mortality of adult coho salmon. Waters were monitored
from 4 to 6 times during the I- and 4-fur exposures, and the results
expressed as ppm-hr dissolved hydrocarbons.

j
TOXICOLOGICAL TESTING OF OIL DISPERSANTS
153
At Battede Pacific Northwest Laboratories, Pearson (1985) stud-
ied the effect of Pru~hoe Bay crude of} and chemically dispersed oil
on Pacific herring egg fertilization, hatching, and larval abnormalities
using a flow-through system. Anderson et al. (1987) of Battelle mea-
sured acute toxicity of the WSF and chemically dispersed Pru~hoe
Bay crude of} to coonstripe shrimp (Pandalus dance), Pacific herring
(Clupea harengus pallasi), and sand lance (Ammodytes hexapterus).
Constant concentrations of of} were selected using a flow-through
system and determining the time (from 12 to 96 hr) to 50 percent
mortality. Dissolved hydrocarbons were monitored. These bioassays
showed little difference in toxicity between total Cal to Cal hydro-
carbons from Pru~hoe Bay crude of! and dispersed oil. The one
exception is the 4 ppm-hr exposure from the WSF of untreated
of} that caused half kid of coonstripe shrimp larvae, which is not
clearly accounted for. Otherwise, the toxicities, based on the Cat to
C~0 hydrocarbon fraction, were about the same from untreated and
chemically dispersed oil. Dissolved hydrocarbons were monitored in
both Battelle studies referenced in Table 3-15.
The WSF of physically and chemically dispersed of} to Artemia
nauplli with Lago Media crude of} and Conceit 9527 was compared by
Mackay and Wells (1980, 1981~. The toxicities were similar. Physical
dispersion was a little more toxic than chemical dispersion. Greater
toxicity to the dissolved hydrocarbon fraction from untreated oil than
from chemically dispersed oil was also observed by Foy (1982) . The
opposite was observed by Duval et al. (1980, 1982) for the isopod G.
Oregonensis using a crude of} (Table 3-15~.
Other studies that measured the dissolved hydrocarbons or
added pure hydrocarbon components individually include Morrow
et al. (1975), who studied young coho salmon and individual hydro-
carbons, and Strnhsaker et al. (1974), who tested benzene and the
eggs and larvae of Pacific herring and northern anchovy in 24-hr ex-
posures. These additional studies generally showed less toxicity than
found by Rice and coworkers.
Table 3-15 supports the following observations:
.
The field exposures in the water column for both untreated
and chemically dispersed oils generally are much lower than expo-
sures required to cause mortality or behavioral effects on a large
number of species and life stages.
· The dissolved hydrocarbons from the WSF of untreated oil
and chemically dispersed oil produced similar organism mortalities.

154
USING OIL SPILL DISPERSANTS ON THE SEA
Dispersed of] was about twice as toxic to chum salmon fry compared
with dissolved hydrocarbons from untreated oil.
Coonstripe shrimp, sand lance, and Pacific herring larvae
were about the same sensitivity. Artemia nauplli and an isopod were
also affected to about the same degree by dissolved hydrocarbons
from dispersed oil.
Summary
The laboratory studies summarized above, comparing lethal and
sublethal toxicities of dispersed of} to various organisms, demonstrate
the wide range of responses that may occur when dispersants have
been used to treat oil, and the many factors influencing the responses.
In general, the results fall into three categories:
1. those employing nominal concentrations (total of} per unit
volume), which find that dispersed of] is more toxic; many (nearly 30
percent) of the tests (usually the earlier ones) fall into this category.
Test results stemming from use of this technique are in error, and
much data are of little use.
2. those analyzing for the water-soluble fraction, which find no
difference in toxicity between physically and chemically dispersed oil;
and
3. those comparing dispersant to dispersed of] toxicity that find
dispersed of] to be more toxic when a relatively nontoxic dispersant
is used, and find dispersant alone to be more toxic when a toxic
formulation is used.
When the WSF of the of} has been analyzed, there is seldom
evidence for synergism (i.e., greater than additive toxicity) between
of] and dispersant components, validating the general conclusion that
of] is as acutely toxic as dispersed oil.
These laboratory studies also demonstrate some of the difficulties
of accurately controlling the exposure of organisms to complex or-
ga~ic mixtures in small tank systems. Such experimental approaches
have been used because they are suitable for specific test organisms,
and because they offer some control over experimental variables. It
is recognized that such approaches do not simulate field conditions.
To date, laboratory studies have been most valuable in exploring the
types of responses and the duration of effects under "high exposure"
conditions, and offering guidance to the design and conduct of field
studies on dispersed oils.

TOXICOLOGICAL TESTING OF OIL DISPERSANTS
MICROBIAL DEGRADATION
155
A potentially important factor for planning dispersant use is
whether it will significantly enhance or retard degradationparticu-
larly microbial degradation of spiced oil. The ultimate fate of
spired petroleum depends primarily on the ability of microorganisms
to use spilled hydrocarbons as sources of carbon and energy (NRC,
1985).
AH marine waters appear to contain mixed natural microbial
populations with the genetic ability to grow on petroleum hydrocar-
bons. However, ocean waters that have continuous of} inputs, as from
seeps or discharges from populated areas, are likely to have greater
numbers and types of oil-degrading microorganisms. Biodegradation
begins after evaporative losses have ceased and continues for a week
to a year. Evidence suggests that chemical or mechanical disper-
sion in the water shortens the time period during which microbial
degradation assists of} removal.
Biodegradation appears to be limited primarily to paraffinic and
aromatic fractions, although studies by Rontani et al. (1986) have
shown some degradation of asphaltenes. To date there is no evidence
of biodegradation of polar fractions, or nitrogen-, sulfur-, and oxygen-
containing compounds (WestIake, 1982~.
Dispersants applied effectively increase the rate and possibly the
extent of biodegradation by
· creating more of} surface area;
· reducing the tendency of of} to form tar bans or mousse
(Gunke} and Gassman, 1980; Daling and Bran~vik, 1988~; and
· enabling dispersed oil droplets to remain in the water column
instead of beaching or sedimenting (Gilfi~n et al., 1985~.
They may also diminish biodegradation rates by
· adding new bacterial substrate (the dispersant) that microbes
might preferentially attack over the oil; or
· increasing concentrations of dispersed of] and dispersant in
the water column, which may have temporary toxic or inhibitory
effects on the natural microbial populations.
Creation of new surface area is the most important factor relat-
ing to biodegradation. Because chemical dispersion of oil increases
surface-to-volume ratios of the oil, and because degradation occurs
at the oil-water interface, the use of dispersants should enhance the
environmental conditions required for suitable microbial growth.

156
USING OIL SPILL DISPERSANTS ON THE SEA
Ideally, key questions relating to possible differences in the rate
and extent of degradation of chemically dispersed and nondispersed
of} should be addressed by direct field comparisons. However, these
comparisons are extremely difficult to accomplish (Green et al.,
1982~. As a result, knowledge of dispersed of! degradation is lim-
ited mainly to laboratory studies, pond and mesocosm studies, and
information on physical and chemical changes that are known to
occur mainly when dispersants act on spilled oil.
Laboratory Studies
Laboratory studies are useful for observing such important phe-
nomena as mechanisms of degradation; changes over time of type and
numbers of oleocIasts petroleum-degrading bacteria (AtIas, 19SS;
Lee et al., 1985~; relative degradability of various petroleum compo-
nents; biodegradability of various commercial dispersants; effects of
nutrient supplements; and enhancement or retardation of degrada-
tion rates with dispersant use. Laboratory studies, including innocu-
lations of field collections, have shown that degradation rates can be
enhanced or inhibited when dispersed of} is added to culture vessels.
For example:
.
TraxIer and Bhattacharya (1978) found that chemical dis-
persants significantly enhanced bacterial degradation of petroleum
hydrocarbons.
· Traxier et al. (1983) found that dispersed of} was more ef-
fectively metabolized by hydrocarbon-utilizing microorganisms than
either untreated of} or dispersant alone.
· Mulkins-Phillips and Stewart (1974) found only slightly en-
hanced degradation upon dispersion.
· Bunch and HarIand (1976) found no difference between un-
treated of} and dispersed oil.
Gatellier et al. (1973) found either enhancement or inhibition
depending on the dispersant used.
Zeeck et al. (1984), using 900 ppm (an extremely high con-
centration) of dispersants, inhibited bacterial growth or decreased
glucose uptake rates.
These widely varying and even apparently conflicting results are
not conflicting, however, given differences in laboratory techniques,
exposure concentrations and durations, nutrient availability in the
culture, temperature, and dispersants and oils tested. Generally, the

TOXICOL O GICA L TESTING OF OIL DISPERSA NTS
157
experiments showing inhibition used dispersant concentrations that
exceeded the range found in field tests.
The biodegradable nature of some commonly used dispersants
has been reported from several laboratory studies (Cretney et al.,
1981; Gunkel, 1974; Traxler and Bhattacharya, 1978~. Because
some dispersants are preferentially utilized over the of} as the carbon
source, some experiments have shown initial of! degradation rates in
the laboratory to be inhibited by the addition of dispersants (Bunch
et al., 1983; Foght and WestIake, 1982; Foght et al., 1983; Mulkins-
PhiDips and Stewart, 1974~. Griffiths et al. (1981) reported decreased
uptake of labeled glucose that appeared to be dependent on disper-
sant concentration. These dispersant-oi} concentrations were higher
than would usually be observed in situ, although Griffiths et al.
(19S1) reported one experiment that showed a 10 percent decrease
observed at 1 ppm. Generally, inhibition has not been important in
pond or mesocosm studies.
The extent to which laboratory studies of biodegradation rate
and extent can be extrapolated to the marine environment is severely
limited. Major problems include the confining conditions of test
vessels and the need to add nutrient supplements. Hydrocarbon
degradation rates from laboratory experiments have been several
orders of magnitude higher than in situ rates. Conversely, toxic or
inhibitory effects are likely to be magnified in the laboratory because
the dispersant and dispersed of} mixtures in the test vessels are not
able to dilute as they would in nature.
Mesoscale Studies
Pond and mesoscale experiments are seen by many researchers
as a way to increase substantially the realism of oil-dispersant ex-
periments. They suffer some of the same shortcomings as laboratory
studies (e.g., a limited water volume), but to a lesser extent. Key
results of several experiments are summarized below. They con-
sistently show enhanced oil degradation rates of dispersed of] over
undispersed of] (see Chapter 4~.
In CEPEX bag experiments reported by Cretney et al. (1981)
and Green et al. (1982), biodegradation was greatly increased in the
dispersed oil bag. Microbial oxidation of the n-alkane component
of the of! was completed within 15 days, a rate at least an order of

158
USING OIL SPILL DISPERSANTS ON THE SEA
magnitude higher than for undispersed of} (Green et al., 1982~. Fur-
thermore, only 0.1 percent of the dispersed of! reached the sediment
during these 15 days, and it was in an advanced state of bacterial
decomposition. At the surface slick in the CEPEX experiments,
microbial degradation had not begun by the end of the 15 days.
In Seafluxes enclosure studies of dispersant and dispersed oil-
stimulated bacterial production, Lee et al. (1985) observed increased
glucose uptake rates in enclosures with dispersant and dispersed oil.
Biodegradation was more important than abiotic processes in the
removal of low volatility n-alkanes of dispersed of! in the Seafluxes
enclosure.
In freshwater pond experiments, alkane degradation rates of
test oils were substantially increased in dispersed of] ponds versus
undispersed oil ponds (Dutka and Kwan, 1984; Dutka et al., 1980;
Green et al., 1982; Scott et al., 1984~. Heterotrophic bacterial counts
increased tenfold in oil-dispersant ponds versus oil-only ponds. Also,
substantially less of} was found in the sediments of the pond treated
with dispersants than in the oil-only ponds after ~ year (Scott et al.,
1984).
In seawater pond experiments, Marty et al. (1979) compared
dispersed and nondispersed of] in 20-m2 (24 x 103 liters) basins
filled with lagoon seawater. Four months after the first treatment,
dispersed slicks were no longer visible, while the untreated reference
slick did not appear significantly different. Nutrients were not added
to the lagoon seawater. Dispersant concentrations were 13 to 130
ppm, significantly higher than manufacturers found in field tests,
even immediately after dispersion.
In dispersant-only tests, oil-degrading bacteria increased by 4 to
100 times those in the seawater only (Marty et al., 1979~. Although
bacterial populations doubled in the oil-only basin after 14 hr of
contact, in the dispersant-treated ponds a doubling was not evident
until the fifth day of treatment. Despite the delay, microbial popu-
lations and extent of degradation were significantly enhanced in the
dispersant tanks after 4 months.
Microbial Field Studies
Bunch (1987) studied the effects of chemically dispersed crude
of} on bacterial numbers and microheterotrophic activity in the water
column and sediments of selected bays at the BIOS experiment site,
Cape Hatt, Northwest Territories, from 1980 to 1983. In the release

TOXICOLOGICAL TESTING OF OIL DISPERSANTS
159
of dispersed of} in 1981, there was a transient decrease in Vmax (max-
imum velocity) of glutamic acid uptake in water samples. Bacterial
numbers were unaffected.
In vitro experunents with water samples demonstrated that a combination
of petroleum and dispersant, or disperse alone, reduced the Vmax of
glutamic acid uptake to a greater extent than petroleum alone.
In addition, total organic carbon and bacterial numbers tem-
porarily increased in the sediments impacted by dispersed oils, re-
covering to normal (control) values by the second year. Effects on the
water column were considered inconsequential or marginally delete-
rious, while effects on the sediment were indirect, long-term, and
likely of marginal significance to microheterotrophic activity.
Summary
Some laboratory studies and all mesocosm studies have shown
increased oil biodegradation rates when dispersants are used. Tem-
porary inhibition of biodegradation with dispersed of} also has been
observed in the laboratory, but appears to occur only at dispersed
of} concentrations higher than would occur in the field. Data from
pond and mesocosm studies strongly indicate that effective use of
dispersants would enhance the biodegradation rate of spilled oil.
With limited field data (Bunch et al., 1983, 1985) available, and
because biodegradation may be slow or incomplete under some field
conditions, this conclusion requires additional verification by field
studies.
The primary objectives of dispersant use are to enhance dilution
effects, to get of} off the water surface, and to prevent stranding of
oil. Hence, any rate enhancement of biodegradation probably should
be viewed simply as a secondary benefit to the primary objectives.
Finally, on the question of whether dispersants enhance the ex-
tent of biodegradation, available information suggests that refractory
compounds would remain undegraded regardless of the addition of
dispersants (Lee and Levy, 1986~. One aspect of this question that
has not been quantified is the extent to which dispersants prevent tar
bad formation. Prevention of tar bass and large mousse accumula-
tions possibly could be an important advantage of chemically dispers-
ing oil, because tar balls, especially large ones, trap biodegradable
hydrocarbons, and mousse accumulations do not break up before
stranding and eventually become buried in intertidal and shallow
subtidal sediments (Jordan and Payne, 1980; NRC, 1985~.

160
USING OIL SPILL DISPERSANTS ON THE SEA
SEABIRDS AND MARINE MAMMALS
Despite concerns of coastal resource managers and of] spill re-
sponse teams about the effects of of} spills on seabirds and marine
mammals, far more research has been conducted on the effects of
oil and dispersed of] on intertidal and subtidal invertebrates, plants,
and fish. Because of high susceptibility to damage and high visibility
when oiled, however, much recent public policy consideration has
been given to seabirds and marine mammals. Unfortunately, many
of the critical questions regarding damage to marine mammals and
seabirds by of} and possible mitigation by dispersants have not yet
been addressed.
There are two primary effects of of] on seabirds and marine
mammals (Leighton et al., 1985; NRC, 1985~:
1. toxic effects resulting from direct ingestion of of! from the
water, or indirectly from grooming or preening; and
2. effects on the water-repellency of feathers or fur needed for
thermal insulation.
Research on toxic effects of ingestion is reviewed below.
Seabeds
The few studies of direct toxicity of of} and dispersants to seabirds
(Table 3-16; Peakall et al., 1987) show that dispersant and crude of!
reduce hatching success and lower resistance to infection to about
the same extent, and sometimes less than, of} ~one. Studies have
been primarily on avian reproduction and physiology. The effects
of of} alone on embryos and early development are well known, and
the effects of oil-dispersant mixtures have been studied at various
stages of the reproductive cycle. Generally, crude oil and Corex~t
9527 mixtures and crude oil alone are similarly toxic to bird eggs,
based on nominal concentrations.
Work with other species, such as mallard ducks and herring gulls
(Table 3-16), also shows a wide range of sensitivities, particularly
with duck eggs. For example, Albers (1979) tested Prudhoe Bay
crude oil, Corexit 9527, and mixtures (5: l and 30:1) on the hatch-
ability of mallard eggs (Anas platyrhynchos) over 6 to 23 days. All
produced diminished hatchability at the 20-pl dose level per egg (ex-
ternal surface). The oil, dispersant, and 5:1 mixture had similar
effects, but the 30:1 mixture was significantly less toxic. At reduced
dosage, only the Cored mixture caused significant effects.

162
USING OIL SPILL DISPERSANTS ON THE SEA
The results of coating experiments are important to note, par-
ticularly for breeding birds, which may transfer dispersant and oil
back to their nests. For example, a field study with Leach's storm
petrels (Butier et al., 1988) showed no effects of internal dosing with
Pru~hoe Bay crude of} or mixtures with Corex~t 9527 (10:1), but
the highest dose of externally applied dispersant-oi] mixture (1.5 m]
per bird) significantly increased the percentage of brooding birds de-
serting the nesting burrow. No significant effects were seen with of]
alone. Hatching success was decreased to the same extent with both
oil and dispersant-oil treatment.
A mathematical model for the exposure of diving and surface-
feeding seabirds to surface oil and dispersed subsurface oil (Peakall
et a]., 1987) led to the conclusion that the exposure resulted from
the surface slick, and that "a highly effective dispersant significantly
reduces of} exposure for both types."
The literature review by Peakall et al. (1987) on dispersed of!
effects on seabirds concluded that the hazard of chem~caDy dispersed
of] to seabirds depended primarily on differing exposures under nat-
uraDy and chemically dispersing conditions. Their evaluation of the
toxicology, based on sublethal responses at the biochemical and phys-
iolog~cal level, showed similar responses to of} components, with and
without dispersants.
Other studies have examined the toxicity of dispersed oils to
seabirds; these include Butler et al. (1979, 1982, 1987), Albers (1980),
Lambert and PeakaD (1981), Miller et al. (1981, 1982), PeakaD and
Miller (1981), Butler and Peakall (1982), Trudel (1984), and Ekker
and Jenssen (1986~. Collectively these studies, including those by
PeakaD et al., show the range of responses of birds to of} and dispersed
oils, the similarity in responses to of] and dispersed oils, and the
obvious need to reduce surface oiling for bird protection.
There are also occasional concerns regarding the direct effects
of the dispersants themselves on seabirds, both on adults and on
eggs and young at the nest. These effects, although perhaps fewer
than those produced by of] itself, include direct accidental spraying
of birds with dispersants (from aircraft) and the potential increased
risk of oiling to seabirds from slicks that have spread after dispersant
application.
The seabird-dispersant issue, following from the above summary,
seems to be one of exposure to the dispersant and the dispersed oil,
rather than one of enhanced toxicity of the oil as perceived until
recently.

TOXICOL O GICA L TESTING OF OIL DISPERSA NTS
Marine Mammals
163
Effects of of} spins on marine mammals include physical fouling,
thermal and compensatory imbalance due to oil coatings, uptake,
storage and depuration of hydrocarbons, changes in enzymatic activ-
ity in the skin, interferences with swimming, occasional mortalities,
eye irritation and lesions, and oiling of young (Engelhardt, l9SS).
Reviews by Geraci and St. Aubin (1980), Smiley (1982), Engel--
hardt (1983, 1985), and NRC (1985) describe the effects of oiling
on the fur of sensitive marine mammals (sea otters), based on lab-
oratory and mesocosm toxicology experiments and observations of
oiled animals in the field. More than a twofold increase in thermal
conductance (over baseline), and therefore a 50 percent reduction
in insulating capacity, has been reported for polar bears (Hurst and
Oritsland, 1982), sea otter pups and fur seals (Kooyman et al., 1977),
live adult sea otters (Costa and Kooyman, 1982), and sea otter pelts
(Hubbs Marine Research Institute, 1986; Kooyman et al., 1977~.
Dispersants have been used experimentally like "shampoos" to
remove crude of! from marine mammal fur, but such attempts re-
moved natural skin oils along with the crude oil, thus destroying the
fur's water-repellency (Williams, 1978~. Surface-active agents, such
as those used in dispersants, can increase the Nettability of fur or
feathers, which in turn allows cold water to penetrate and increase
the thermal conductance of the pelt. This is particularly dangerous
to animals that are buoyed or insulated by their fur or feathers. In the
case of the sea otter, unless grooming can quickly repair the damage,
cold water leaks through the fur and against the skin, causing fatal
chilling. If the animal grooms excessively, however, it can scratch
away large amounts of underfur, further complicating the restoration
of body insulation (McEwan et al., 1974~.
Direct toxicity is also a potential problem. Polar bears died from
toxic effects of oil ingested during grooming (Engelhardt, 1981) as
did river otters examined after an oil spill at Sullom Voe, Shetland
Islands (Richardson, 1979~.
To date, only Hubbs Marine Research Institute (1986) has ad-
dressed chemically dispersed oil effects. The critical work by the
American Society for Testing and Materials (ASTM, 1987) reviews
the literature on oil damage and other human disturbances to marine
mammals, but cites none regarding the effects of dispersed oil.
Attempts to remove oil or dispersed oil from sea otter pelts
showed that any residue of oil or dispersant left on the fur, even
if the fur was dry, permitted water to penetrate into the fur upon

164
USING OIL SPILL DISPERSANTS ON THE SEA
immersion (Hubbs Marine Research Institute, 1986~. This confirmed
the earlier studies of the damaging effects of increased wettability of
sea otter fur after contact with crude oils, detergents, and dispersants
(Costa and Kooyman, 1982~.
Research on thermal responses was conducted by rubbing fresh
oil or 5-day weathered Santa Barbara crude oil on adult California sea
otter pelts (Hubbs Marine Research Institute, 1986~. Fresh oil alone,
or with Correct, easily penetrated the fur, which quickly saturated
upon immersion in water. Thermal conductance was more than
twice as high as in untreated control pelts. There was no difference
in conductance between fresh crude alone or with of} combined with
the dispersant. Based on such sparse information, oil dispersant
chemicals may not reduce the physical threat of spilled of! to some
fur-insulated sea mammals.
Smiley (1982) stated that
Nonetheless, dispersion of large oil slicks is probably a useful countermeasure
tool, assuming that both the floating oil and the applied chemical are
effectively diffused into the water column. The risks of direct fouling and
of inhalation toxicity when swimming at the sea surface would be reduced,
especially in cold icy situations where natural weathering And evaporation
of oil slicks is slow.
In addition, the ASTM (1987) concluded that
Use of chemical dispersants and mechanical methods is recommended to
prevent these habitats from being contaminated or to reduce contamination.
. . . Because sea otters and polar bears are very sensitive to oil contamination,
dispersant use is recommended even if application must occur near or in a
habitat used by these animals.
However, available data do not seem to support this recommen-
dation, and Smiley's conclusion assumes complete dispersion and
disappearance of surface of} after dispersant application, which may
not occur.
In view of the enormous public interest in, and concern for, the
fate of seabirds and marine mammals, it is surprising that so little
research with dispersants has been done with these animals, and
that the conclusions on the use of dispersants for protecting these
animals can only be tentative. Clearly, there is a great need for
more laboratory and field studies, particularly in order to determine
whether the use of dispersants wiD lessen the adherence and impact of
of] on the fur of marine mammals and the feathers of birds. Thus far
the data only appear to indicate that there is no difference between
the effects of oft with dispersants or alone.

While major oil spills are rare, oil slicks can have disastrous environmental and economic consequences. This book summarizes research on the use of chemical dispersants: their effectiveness and limitations and the results of using them in different spill situations. Based on laboratory and field research as well as on actual case histories, this book contains a clear-cut set of recommendations for action, planning, and research. Of special interest is the chapter on the biological effects of oil itself and of oil treated with chemical dispersants.

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